Automatic freeness tester



INVENTCRS DONALD w. DANFORTH, WILLIAM RICHARD CLENDANIEL By PM "7 v ATTORNEYS D. W. DANFORTH ET AL AUTOMATIC FREENESS TESTER Jul 1, 1969 Filed Nov.

3,452,587 AUTOMATIC FREENESS TESTER Donald W. Danforth and William Richard Clendaniel,

Audover, Mass, assignors to Bolton-Emerson, Inc.,

Lawrence, Mass., a corporation of Massachusetts Filed Nov. 21, 1966, Ser. No. 601,278 Int. Cl. Gllln 11/10 US. or. 73- 63 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved paper pulp freeness tester, especially of the Canadian standard laboratory type approved by the Pulp and Paper Research Institute of Canada and well known in the art.

The Canadian standard freeness tester includes a perforated plate, or screen, at the bottom of the drainage chamber which is standardized and can be compared with a plate certified by the above-mentioned institute. It is also approved in the United States by TAPPI, as TAPPI Standard 227.

The freeness tester device stipulated by TAPPI Standard 227 consists of an upstanding, fixed drainage chamber, having a rate-measuring funnel therebelow, there being a bottom screen, a bottom hinged lid, a top hinged cover, and a vent petcock in the cover. At present, the accepted and standardized testing procedure involves a laboratory technician drawing off a sample of paper stock, taking the sample to the laboratory, and pouring the sample into the drainage chamber. Usually the sample is shaken for agitation before pouring, and such shaking varies with each successive test and with each operator.

At the time of pouring, the bottom lid is closed. After pouring, the cover is closed for sealing the chamber and the vent is also closed. TAPPI Standard 227 specifies that an interval of five seconds must transpire from the end of pouring the sample to the opening of the vent petcock.

It has been found that, if this time interval is made shorter, or longer, by only a few seconds, an error of as much as cc. can easily result. In addition, whereas TAPPI 227 does not specify pour time, a difference between a relatively fast and slow pour can result in an error of more than 10 cc. These differences are generally greater for freer stocks and less for slower stocks.

If these two time intervals are always kept precisely the same, substantially similar determinations will result (presuming, of course, identical samples). However, in the paper mill it is quite unlikely that the same, or different, individuals will manually shake each sample, pour the same, and time the settling of the sample in an identical fashion. Inasmuch as such possible human errors are algebraically additive, it can be seen that an error of as much as cc. is quite possible.

In this invention, all such human errors, or inconsistencies, are eliminated by automating the freeness tester to follow an exact predetermined cycle which is identical for each pulp sample tested. The standard laboratory freeness tester is provided with a cover equipped with a suitable agitator, movable in a predetermined path within the filtration chamber, a powered vent valve and a powered bottom lid release, together with automatic cycling means controlling the same. Thus, with the bottom lid and vent valve closed, the operator pours the sample into States Patent 0 the filtration chamber without regard for pour time, closes the cover and initiates the cycle. Thereupon automation takes over and the agitator is submerged and lifted in the pulp sample, without rotation, for a pre determined time, or number of strokes, five seconds elapses after the termination of agitation, the bottom lid is released and the vent valve opened to drain the filtrate through the screen. Each sample is subject to identical treatment and conditions so that the utmost accuracy and reproducibility is achieved.

We are aware that it has herebefore been proposed to provide a rotary sinker in the filtrate chamber as in US.

Patent 1,985,321 to Green of Dec. 25, 1934, this being in rear of the filtration chamber. Also that in US. Patent 1,970,521, to Harvey of Aug. 14, 1934, a rotary impeller is provided in a mixing chamber in advance of the filtration chamber. It has also been proposed in U.S. Patent 2,022,010, to Schopper, of Nov. 26, 1935, to release the bottom lid, or valve, by lifting it through the pulp mixture in the filtration chamber, while in US. Patent 2,346,945, to Samson, of Apr. 18, 1944, a piston rides down the filtration chamber on the pulp sample to apply constant pressure on the sample. As far as we are aware, however, no freeness tester of the prior art discloses an agitator element, movable in a predetermined path through a pulp sample in a filtration chamber, for identically and randomly dispersing the fibres therein, and none discloses the fully automatic cycle control apparatus taught herein for entirely avoiding human error in pulp testing.

The principal object of the invention is to provide a fully automatic, laboratory type freeness tester, which subjects each successive pulp sample placed therein to identical agitation and identical conditions.

Another object of the invention is to provide, in any type of pulp freeness tester, an automatic, powered agitator operable in the zone just in advance of the screen, for thoroughly dispersing the fibres in the stock with random substantially identical distribution prior to each successive test for freeness.

A further object of the invention is to provide an automatically controlled freeness tester for eliminating human error which achieves a close correlation of successive tests by means of apparatus attachable to existing laboratory testers.

Other objects and advantages of the invention will be apparent from the claims, the description of the drawings, and from the drawings, in which:

FIGURE 1 is a front elevation of a preferred embodiment of the invention, partly in section;

FIGURE 2 is a side elevation thereof, partly in section;

FIGURE 3 is a plan view thereof in section on line 33 of FIGURE 2;

FIGURE 4 is a plan view thereof in section on line 4-4 of FIGURE 2;

FIGURE 5 is a plan view thereof in section on line 55 of FIGURE 2; and

FIGURE 6 is a schematic electric diagram of the cycle control and power circuits of the invention.

As shown in the drawings, a preferred embodiment of the automated freeness tester of the invention is designated 35, and includes most of the conventional elements of the laboratory type testers now much in use in the paper art. Such conventional parts include the upstanding vertical tube 36, which defines the filtration, or drainage, chamber 37 therewithin, extending from the top opening 38 to the bottom opening 39, the screen 40, which is a stand: ardized perforated, brass plate, and the heavy, bronze bottom lid 41, hinged at 42 on one side of the cylindrical tube 36 and latched at 43 on the other side of the tube 36. The cylindrical tube 36 is fixed with its central longitudinal axis vertical by means of a suitable wall bracket 44, so that screen 40 is horizontal. A filtrate receptacle 45,

in conventional, rate-measuring funnel form, is fixed to bracket 44, under screen 40 to receive the filtrate, and both the filtration chamber 37 and the filtrate receptacle 45 are held exactly level. The bottom lid 41 is resiliently gasketed to seal the pulp sample chamber 37. As thus far described, the tester 35 is standard, and the cross-sectional area, diameter, and height of filtration chamber 37 are determined in accordance with accepted standards.

In this invention, the perforated screen 40 is coated with, or formed of, a fluoroplastic to form a fluoroplastic surface 30, preferably of polytetrafluoroethylene' (TFE) although it may be any one of the commercially available fiuoro carbons or fiuoroplastics such as fiuorinated ethylcue-propylene (PEP) or polyvinylidine fluoride (VFZ). While the paper stock being tested would be expected to be a good lubricant so that the fibres would not stick in the holes of a screen, in practice such sticking sometimes oc' curs and requires repeated cleaning of the screen. It has been found, however, that the screen 40 with the fluoroplastic surface 30 of this invention eliminates sticking of the fibres even when the paper stock contains sticky coating fillers, abrasives or active chemical ingredients. It is believed that the surface 30 has a more acute angle of wetting which may reduce surface contact of the fibres with the screen.

The conventional laboratory tester has a heavy bronze cover, similar to the bottom lid 41, for closing and sealing the top opening 38, there being a suitable resilient gasket, hinge mounting and manually operable latch for achieving an airtight closure. An air cock is also provided in the conventional cover by which air can be admitted at the start of each test. In this invention, the conventional cover is replaced by the openable, sealing cover 48, which is hingedly mounted at 49, gasketed at 50, and manually latched at 51, but the cover includes an axial bore 52, having a tapered, annular seat 53, and having a recess 54 of predetermined capacity to compensate for the volume of an agitator rod 55 slidable in the bore. The standardized filtration chamber 37 is four inches in diameter and five inches in height to contain a predetermined capacity of pulp sample between the upper face 56 of screen 40 and the rim 57.

Agitator means 60, preferably in the form of a disclike plate 61, is mounted within the filtration chamber 37, in the recess 54, and fixed to the terminal end 62 of agitator rod 55, the plate 61 being horizontal, symmetrical, and of predetermined area and diameter with relation to the area and diameter of the chamber to loosely fit therein. The portion 63 of rod 55, extending outside chamber 37 is of sufficient length, such as, at least five inches, to permit the rod to move the plate 61 along the longitudinal axis of the chamber from the level of the pulp sample therein at rim 57 down through the sample to the level of the face 56 of screen 40 and up again, to thoroughly disperse the fibres in random distribution. The upper face 64 of agitator plate 61 includes a tapered, resilient sealing element 65, which fits securely in the seat 53, when the rod 55 and plate 61 are lifted above their normal Path, to thereby form a normally open vent valve for filtration chamber 37.

Fixed to cover 48, by suitable bolts 67 is powered actuation means 68 which includes the housing 69, pivotable with the cover when opened or closed. The powered actuation means 68 is preferably a solenoid'linear actuator, of a commercially available type such as a Polynoid made by Skinner Precision Industries, Inc., of New Britain, Conn. Agitator rod 55 extends through the solenoid stator coil 71, which is fixed in the stator chamber 72, and the upper end 73 of rod 55 is connected to a pair of rolled coil springs 74 and 75. A boss 77 on rod 55 trips limit switch 78 at the top of the agitation stroke and trips limit switch 79 at the bottom of the agitation sroke.

Powered actuation means 68 is external of the filtration chamber 37, and it will be seen that energization of solenoid stator coil 71 will drive the rod 55 downwardly, and

submerge the agitator plate 61 downwardly through a pulp sample in chamber 37 from top to bottom thereof. The clearances are such that the plate 61, in moving down the central longitudinal vertical axis of the chamber, agitates the pulp without constituting a close-fitting piston head applying compressive pressure. Upon tripping limit switch 79 at the bottom of the stroke, solenoid stator coil 71 is de-energized whereupon the coiled springs 74 and 75 lift the agitator plate 61 and rod upwardly through the sample until limit switch 78 is tripped to start another downward stroke.

Preferably agitator plate 61 contains a predetermined pattern of apertures 80, each of substantial area, to ease the passage of the plate through the liquid while avoiding stapling of fibres on the rims of the apertures.

While a separate automatically operated vent valve could be used, as explained above, the plate 61 itself is preferred as the powered vent means 82, by making use of the resilient sealing face and valve seat 53. After a predetermined number of up and down agitation strokes along the predetermined path of agitation, the solenoid stator coil is so energized as to force the rod 55 upwardly above the agitation path to seal the chamber 37. The bottom lid latch may then be released, with suction preventing filtrate from passing through screen 40 until the powered vent means 82 is opened automatically in the cycle.

Powered bottom lid release means 83 is provided in the form of a latch release rod 84, mounted for vertical movement in a second solenoid stator coil 85, the upper tip 86 of the rod 84 lifting the latch 43 on its powered upward stroke.

The automatic cycle control means 88 of the invention includes a commercially available motorized timer having a thirty-six step rotor, which actuates a series of cams one step each. Twelve steps are used in each cycle of this invention, so that three twelvestep programs are secured on one revolution of the rotor cam.

In operation, the bottom lid 41 is manually closed, latched and sealed, the pulp sample poured into filtration chamber 37 up to rim 57, and the top cover 48 is closed and latched. Agitator plate 61 is normally poised in recess 54, above the level of the sample and below the bore 52, so that the chamber is vented to the atmosphere. Start switch 89, of automatic control system 88 is then closed to automatically operate the apparatus through its predetermined cycle without human intervention, error, or inconsistency. The energization of the control system, by switch 89 causes steps 1 to 12 of the cycle to take place, steps 13 to 24 and steps 25 to 36 each being a duplicate set of steps. On step 2, the solenoid 71 is energized to drive the rod, or core, 55 down, thereby submerging plate 61 to the level of screen 40, and agitating the pulp sample. The closing of limit switch 79 de-energizes the circuit to permit springs 74 and to lift plate 61 through the sample for further agitation, the closing of upper limit switch 78 again energizes the solenoid 71, and the downward vertical strokes continue as steps 4. 6, 8, and 10 until the end of upward step 11, at which time the plate 61 is lifted by the springs to the top of the pulp sample to its initial position. The solenoid coil 71 is then energized to drive rod 55in the opposite, or upward, direction by the timer relays, thereby causing plate 61 to seal the bore and make chamber 37 air-tight. The solenoid coil 85, in step 12, is then energized to drive the lid release rod 84 upwardly to unlatch and open the bottom lid. At the end of the standardized time interval of five seconds, the timer then de'energizes solenoid coil 71 to open the automatic vent means 82 and permit the filtrate to pass through screen 40 into the filtrate receptacle 45.

It is within the scope of this invention to mount the apparatus upside down, and in a single tube, so that the screen 40 divides the tube into a lower filtration chamber on one side thereof and an upper filtrate chamber on the other side thereof. The agitator plate 61 will thus reciprocate axially in the lower filtration chamber and pneumatic means may be used to close all the filtration chamber from a source of pulp to be tested, such as a closed stock line, to admit a pulp sample into the chamber for agitation and to draw the filtrate through the screen upwardly into the filtrate chamber, all on a predetermined cycle. In a laboratory type test, the sample could be poured into a lower filtration chamber, agitated as taught herein, and suction then applied to the upper filtrate chamber for measuring rate of drainage, thereby eliminating the need for an air vent means in a cover and eliminating the need for a releasable lower lid.

A schematic circuit diagram of the stepping relay and timer used in the apparatus of the invention is shown in FIGURE 5, wherein the 115 v. source is designated 90 and the timer motor 91, and a rectifier diode 92 are in circuit therewith. A rectifier 93 converts the source to 115 v. DC with the operating coil 94 of the stepping relay in the direct current circuit 95, while the solenoids 71 and 85 are in the AC circuit 90. 96 is an interrupter for the coil 94, 97 is a four pole, three hole toggle switch, 98 and 99 are condensers, and 100 designates pilot lights. Timer switches are designated 102, 103 and 104, and cam switches are designated 105, 106, and 107.

What is claimed is:

1. An automated paper pulp freeness tester of the type having a filtration chamber with a screen at the bottom; an operable bottom, sealing lid, an openable, top, sealing cover, and a rate-measuring filtrate receptacle mounted under said bottom lid, said tester comprising:

agitator means, mounted for movement in a predetermined path, within said filtration chamber, from top to bottom of a pulp sample therein; powered actuation means mounted externally of said chamber and operably connected to said agitator means for driving said agitator means successively and identically on said predetermined path;

powered vent means associated with said cover for sealing and unsealing said filtration chamber;

powered bottom lid release means mounted externally of said chamber and operably connected to said bottom lid for opening the same, and

automatic cycle control mechanism operably connected to said actuation means, vent means and release means, said mechanism driving said agitator means on said path through a predetermined cycle, then releasing said bottom lid, and then venting said chamber to deposit the contents of said chamber in said rate-measuring filtrate receptable.

2. An automatic paper pulp freeness tester as specified in claim 1, wherein said agitator means comprises a symmetrical agitator plate, supported at the terminal end of an agitator rod, said rod being vertically slidable in an axial bore in said cover and adapted to reciprocate said plate axially on a rectilinear path,

whereby said plate imports no rotative, or vortical,

forces to the fibres in said pulp and disperses said fibres in random distribution.

3. An automated paper pulp freeness tester as specified in claim 2 wherein said symmetrical agitator plate includes a predetermined pattern of apertures therethrough and is of predetermined area, slightly less than, but conforming in figuration with, the cross-sectional area of said filtration chamber,

whereby substantially all of the fibers in the pulp sample within said filtration chamber are agitated by said plate in its passage along said path.

4. An automated paper pulp freeness tester as specified in claim 2, wherein said agitator means comprises a horizontal agitator plate within said chamber, fixed to the terminal end of an agitator rod extending through an axial bore in. said cover, said plate having a beveled, resilient upper face and said bore having a seat for said face, and

said powered actuation means includes power means for moving said plate upwardly out of said predetermined path to cause said beveled resilient face to hermetically seal said bore,

whereby said face and bore constitute said vent means.

5. An automated paper pulp freeness tester as specified in claim 1, wherein said agitator means is a horizontal, circular plate movable within said chamber from top to bottom thereof, said plate having an agitator rod extending through an axial bore in said cover to form a core, and

said powered actuation means comprises a solenoid type, electric-conducting, coil for driving said core to move said plate along said predetermined path.

6. An automated paper pulp freeness tester as specified in claim 1, wherein said agitator means is a circular horizontal agitator plate of slightly less diameter than the diameter of said drainage chamber,

said powered actuation means is an electric coil of the solenoid type arranged to move said plate downwardly along said path in response to energization by said control mecahnism, and

said actuation means includes return spring means arranged to move said plate upwardly along said path upon each de-energization of said coil.

7. An automated paper pulp freeness tester as specified in claim 6, wherein said powered bottom lid release means includes a second electric coil of the solenoid type encircling an axially extending lid release rod and arranged to move said rod upwardly to release said lid in response to energization of said second coil by said control mechanism, said release rod moving downwardly by gravity upon de-energization of said second coil.

8. A laboratory type, paper pulp freeness tester, automated to be free of human error, said freeness tester comprising a fixed, hollow, cylindrical, upstanding tube having a filtration chamber therein, having a screen fixed horizontally across said chamber, and having a hinged, latched bottom lid under said screen;

a hinged, latchable, top sealing cover having an agitator rod vertically slidable in a central aperture therein, said rod having a circular, agitator plate at the lower terminal end thereof extending horizontally within said chamber when said cover is in closed, latched position, said rod extending outside said cover for sufficient length to permit reciprocation of said plate from top to bottom of the pulp sample in said chamber;

' a valved vent in said cover;

a bottom lid latch release member;

power means for reciprocating said agitator rod, opening said vent valve and moving said release members, and

automatic cycle control mechanism operably connected to said power means, for actuating the same in accordance with a predetermined cycle,

whereby each pulp sample tested in said chamber is subjected to identical treatment for identical periods of time.

9. An automatic freeness tester for paper pulp, said tester comprising a fixed, vertical, tube having a horizontal screen fixed thereacross, said tube having a pulp sample filtration chamber on one side of said screen and a filtrate receptacle on the other side of said screen;

a horizontal agitator plate mounted within said filtration chamber for vertical axial reciprocation therein from top to bottom thereof, free of rotation around said axis;

powered actuation means, mounted externally of said filtration chamber, and operably connected to said agitator plate, for alternately submerging and lifting said plate in a pulp sample contained in said chamber, and

automatic cycle control mechanism operably connected to said powered actuation means for subjecting each successive pulp sample in said chamber to an identical cycle of agitation by said plate.

10. A freeness tester as specified in claim 9, plus releasable tube closure means normally separating said filtrate receptacle from said screen, said means including powered release means for initiating release thereof to permit passage of filtrate through said screen into said filtrate receptacle,

said powered release means being operably connected to said automatic cycle control mechanism for initiating said release at the termination of each said cycle of agitation.

8 11. A freeness tester as specified in claim 9 wherein: said screen includes an exposed surface formed of fluoroplastic,

whereby the sticking of fibres in said pulp to the apertures in said screen is eliminated despite repeated use of said screen in said automatic testing.

References Cited UNITED STATES PATENTS 8/1934 Harvey 73-63 3/1951 Qveflander 73-63 US. Cl. X.R. 

